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The difference between Linewidth and Bandwidth in laser

odawnw

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Linewidth and Bandwidth - It's very difficult for me to distinguish between these two parameters in laser, at first I think they must be identical, but, after checking the definition, I find that I am confused.

Let's take an example.
Now that I need the laser to produce a beam which has a full width at half maximum (FWHM) within 0.112237 [nm], and the corresponding frequency might be 2.67106620811e [EHz], there is no doubt that this is the bandwidth of of my requirement.
however, according to the specification of many laser systerms, their linewidth might be only within MHz (some might be in GHz, but rare), may I understand that these laser cannot meet me requirement?

I would like to hear your suggestion.
Thanks!
 

RedCowboy

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Bandwidth is basically how much information it can carry.

A 405nm Blu-Ray has more wave fronts per inch than a 660nm red, thus more digitized information can be carried per inch on a 405nm beam than a 660nm beam as they both move at the same speed, the speed or light, but the lower the number ( NM ) the higher the frequency and the more bandwidth.

405 nm is the actual length of the wave as 660nm is the length of that wave, so the 405 has more waves per given length/duration of time.

This is why South Korean internet is so fast, it's using a lot of optical fiber, while they invested in fiber our infrastructure invested in wireless.

In what context are you using linewidth? That can mean different things.




 
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odawnw

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Bandwidth is basically how much information it can carry.

A 405nm Blu-Ray has more wave fronts per inch than a 660nm red, thus more digitized information can be carried per inch on a 405nm beam than a 660nm beam as they both move at the same speed, the speed or light, but the lower the number ( NM ) the higher the frequency and the more bandwidth.

405 nm is the actual length of the wave as 660nm is the length of that wave, so the 405 has more waves per given length/duration of time.

This is why South Korean internet is so fast, it's using a lot of optical fiber, while they invested in fiber our infrastructure invested in wireless.

In what context are you using linewidth? That can mean different things.
thanks for your reply
For my above example, I focus on the laser spectrum's phase only, but not any information carried inside.
To make it clear, I would like to elaborate my example as a plot below, let's assume the plot below is the desired spectrum I hope that I can get from the laser I buy with a laser producer

The full width at half maximum (FWHM) in this plot is the black horizontal line, ignoring the axis (actually this is a photo I find in Google image) let's say the line's width is 0.112237 [nm], which is 2.67106620811e [EHz] according to the formula in https://www.rp-photonics.com/bandwidth.html

The question now is that, nearly no laser producer offer the parameter in this aspect, all they offer are only linewidth, but in this case, can a linewitdh equal to the bandwidth?
 
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RedCowboy

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Multimode diodes can produce side bars that are of the adjacent wavelength to the dominate wavelength, single mode would be more narrow.

 




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